With the reduced thicknesses and sizes of apparatuses, there has been a strong demand for an increase in the mounting density of electronic circuit devices having an insulating circuit board on which resistors, capacitors, semiconductor elements, and the like are mounted.
For electronic circuit devices of this kind, the component mounting density has been increased by reducing wiring pitch or stacking a plurality of electronic circuit boards together.
For example, an electronic circuit device described in Japanese Patent Laid-Open No. 2001-177235 (Patent Document 1) has a base printed circuit board 310 and a module circuit board 350 stacked on the base printed circuit board 310 via spacers 360 as shown in FIG. 25.
The spacers 360 are temporarily fixed to the upper and lower circuit boards via spherical solders 380 and 390; the spherical solders 380 are electrically connected together through via holes 320, and the spherical solders 390 are electrically connected together through via holes 320. The spacers 360 temporarily fixed between the base printed circuit board 310 and the module circuit board 350 are all subjected to reflow soldering at a time. Reference numeral 330 denotes a surface mounting component mounted on the module circuit board 350. Reference numeral 340 denotes a semiconductor bare chip mounted on the module circuit board 350.
An electronic circuit device described in Japanese Patent Laid-Open No. 2001-267715 (Patent Document 2) has electronic circuit boards 410 and 430 laid on top of each other via a heat-resistant elastic member 400, the outer periphery of which is coated with a conductive substance, as shown in FIG. 26. The heat-resistant elastic member 400 is soldered to a connecting land 420 on the one electronic circuit board 410 and contact-bonded to a connecting land 440 on the other electronic circuit board 430 by a clip, a bolt 470, or the like. Reference numeral 450 denotes a surface mounting component, and reference numeral 460 denotes a semiconductor bare chip.
An electronic circuit device described in Japanese Patent Laid-Open No-6-260736 (Patent Document 3) has a module circuit board 500 mechanically and electrically connected to a mother board 540 via connecting chips 550 as shown in FIG. 27. Reference numeral 510 denotes an IC package, and reference numerals 520 and 530 denote passive components.
An electronic circuit device described in Japanese Patent Laid-Open No. 2001-245186 (Patent Document 4) has a three-dimensional printed circuit board 600 in which a lens 660, an optical filter 670, a semiconductor image pickup element 610 are integrally incorporated on an optical axis of the lens 660 as shown in FIGS. 28A and 28B. The three-dimensional printed circuit board 600 has a wiring pattern 650 that allows the semiconductor image pickup element 610 and a chip component 615 to be connected together. Reference numeral 640 denotes a printed circuit board to which the three-dimensional printed circuit board 600 is soldered for mounting.
An electronic circuit device described in Japanese Patent Laid-Open No. 2000-341566 (Patent Document 5) has the three-dimensional circuit board 600 on which the semiconductor image pickup element 610 and an infrared filter 680 are installed and which is mounted on the circuit-integrated printed circuit board 640 as shown in FIGS. 29A, 29B, and 29C.
Another method uses connectors, which are general connecting components, for junction.
Furthermore, for example, an electronic circuit device described in Japanese Patent Laid-Open No. 6-61415 (Patent Document 6) has a plurality of circuit modules stacked via solder or the like using a terminal 720 projecting from a side surface of a circuit module 710 as shown in FIG. 30. The circuit module 710 has the terminal 720 projecting from the side surface toward a bottom surface of the circuit module. Another circuit module 730 located under the circuit module 710 has a terminal portion 740 projecting from a general side surface so as to form an L shape.
The circuit module 710 and the circuit module 730 are joined together by joining the terminal portion to the L-shaped terminal portion via a joining member such as solder.
An electronic circuit device described in Japanese Utility Model Laid-Open No. 1-134367 (Patent Document 7) has a circuit board 810 and another circuit board 820 which are stacked via anisotropic conductive rubber 830 and connected together using a fastener 840 as shown in FIG. 31.
In spite of continuous efforts to improve the functions of the portable terminal devices and to reduce the thickness and size thereof, two-dimensional electronic circuit devices are limited in improvement of the mounting density based on a reduction in connecting pitch and in the gap between adjacent components. Attempts have thus been made to three-dimensionally stack module circuit boards together to increase the density.
The spacers 360 in (Patent Document 1) and the connecting chip 550 in (Patent Document 3) three-dimensionally connect the module circuit boards together via the conductive vias or via holes 320 that connect the lands formed on the upper surface of the circuit board to the corresponding lands formed on the lower surface of the circuit board.
If the clip 470, the bolt, or the like is used to fix the stacked module circuit boards in (Patent Document 2) together, an area occupied by fixing and connecting members increases to reduce mounting area. Furthermore, the number of connecting terminals between the module circuit boards increases to increase the area of the connectors used to connect module circuit boards together. This disadvantageously prevents the mounting density from being increased by increasing the connecting area between the module circuit boards.
The three-dimensional printed circuit board 600 in (Patent Document 4) and (Patent Document 5) includes the disclosed three-dimensional wiring structure of the image pickup element 610 and is three-dimensionally connected to the printed circuit board 640 via the solder 620. However, the reliability of the connections cannot be improved simply by soldering the wiring pattern 650 on the printed circuit board 640 to the tip portions of the land electrodes 630 on the three-dimensional printed circuit board 600, formed on the surface of the circuit board.
The terminal portion 720 in (Patent Document 6) is three-dimensionally joined to the L-shaped terminal portion 740 via a joining member such as solder. When the fastener (clip) 840 or the like is used to fixedly stack the circuit boards in (Patent Document 7) together, the area and height occupied by the fixing and connecting members increases to reduce the mounting area (volume). Furthermore, the number of connecting terminals between the module circuit boards increases to increase the area of the connectors used to connect the module circuit boards together. This disadvantageously prevents the mounting density from being increased by increasing the connecting area between the module circuit boards.
Further, recent portable devices have been desired to offer durability and reliability against a fall or the like. Thus, the reliability of the connection cannot be improved by making the connections only by solder as in the case of (Patent Document 6).
An object of the present invention is to provide an interconnecting board which solves the conventional problems and which provides dense mounting and improved connection reliability.